As a conventional method of fabricating a semiconductor device, a method of fabricating a semiconductor device having a wiring structure in which a barrier film for suppressing Cu-diffusion is formed in a self-aligned manner between a wiring main body layer mainly comprising Cu and an interlayer insulating film. For example, Japanese Patent Laid-Open No. 2005-277390 discloses such a method of fabricating a semiconductor device.
This barrier film mainly comprises a compound of a predetermined metallic element such as Mn and a constituent element of the interlayer insulating film. Since this predetermined metallic element easily forms an oxide, when a reactive layer is once formed, a reaction rate of the oxygen from the insulating film with the metallic element becomes extremely slow. Therefore, a substantial reaction does not advance, so that the homogeneous, super thin and stable barrier film is formed between the wiring main body layer and the interlayer insulating film.
According to this method of fabricating a semiconductor device, a Mn—Cu alloy film, for example, is formed in a wiring trench formed at the interlayer insulating film, and a Cu film which is a material of the wiring is deposited thereon. The barrier film is formed between the Mn—Cu alloy film and the interlayer insulating film by carrying out heat treatment on the Mn—Cu alloy film and the Cu film. Simultaneously, Mn diffuses in the Cu film, and is precipitated as the insulating film mainly comprising a Mn oxide at a surface of the Cu film. Mn can be removed from the Cu film by removing the insulating film mainly comprising the Mn oxide.
However, according to this method of fabricating a semiconductor device, since a Cu film is deposited to have a thickness of 0.8 to 1.0 μm, when the insulating film mainly comprising the Mn oxide is precipitated on the surface of the Cu film, a part of Mn does not reach the Cu film surface and may remain within the Cu film. The residual Mn causes the increase in a specific resistance of the wiring as impurity metal.
In addition, according to this method of fabricating a semiconductor device, it is also possible to use a technique of carrying out a heat treatment to form a barrier film before depositing the Cu film on the Mn—Cu alloy film. However, according to this method, the Cu film formed on a surface of the barrier film aggregates when the barrier film is formed, so that a Cu film deposited on the barrier film may be peeled off.